Ringless spinning of separated staple fibres

ABSTRACT

A rotary spinning chamber is provided having on its inner circumference an annular groove surrounding its axis of rotation and being delimited by two mutually inclined surfaces. Separated staple fibers are admitted into the spinning chamber to form in the recess a sliver having a triangular cross section, a shorter and a longer side of which have a ratio of between 1:1.5 and 1:5. The sliver is withdrawn from the chamber during rotation in such a manner that it will initially move along an inner surface of the chamber to be imparted twist by friction with respect to the surface, and thereupon along the axis of rotation of the chamber to be imparted additional twist due to the rotation of the chamber with reference to the portion of the sliver which is being withdrawn and thus becomes converted into a yarn.

United States Patent 191 Marsalek et al. I I

111 3,812,667 14 1 May2 8, 1974 RINGLESS SPINNING OF SEPARATED STAPLE FIBRES [75] Inventors: Milan Marsalek; Jan Junek; Vaclav Brynda; Frantisek Burysek: Frantisek Hortlik; Josef Ripka; Jiri Lanta, all of Usti nad Orlici, Czechoslovakia [73] Assignee: Vyzkumny Ustav Bavlnarsky, Usti nad Orlici, Czechoslovakia [22] Filed: Mar. 6, 1972 [21] Appl. No.: 231,833

[30] Foreign Application Priority Data Mar. 5, 1971 Czechoslovakia 1650-71 [52] US. Cl 57/58.89, 57/58.95, 57/156 [51] Int. Cl Dillh l/l2 ['58] Field ofSearch.......57/58.89, 58.95, 58.91, 156

[56] References Cited UNITED STATES PATENTS Stary et al 57/58.89 3,481,128 12/1969 Landwehrkamp et a1..... 57/58.95 x

3,501,905 Landwehrkamp et al. 57/58.89

3/1970 3,520,122 7/1970 Shepherd 57/58.89 3,523,300 8/1970 Tabata et al 57/58.91 3,604,194 9/1971 Edagawa et al 57/58.89

Primary Examiner-John Petrakes Attorney, Agent, or FirmMichael S. Striker [5 7] ABSTRACT 1:5. The sliver is withdrawn from the chamber during rotation in such a manner that it will initially move along an inner surface of the chamber to be imparted 1' twist by friction with respect to the surface, and thereupon along the axis of rotation of the chamber to be imparted additional twist due to the rotationof the chamber with'reference to the portion of the sliver which is being withdrawn and thus becomes converted intoa yarn.

12 Claims, 9 Drawing Figures FATENTED HAY 2 8 I974 SIEETZDFZ RINGLESS SPINNING OF SEPARATEI) STAPLE FIBRES BACKGROUND OF THE INVENTION The technique of converting separated staple fibers into a yarn by ringless spinning is already well known. Generally speakingit is carried out by rotating a substantially cup-shaped rotary spinning chamber about an axis which intersects the opposite axial ends of the spinning chamber, one of which ends is open. Separated staple fibers are admitted into the open end of the spinning chamber and become deposited by centrifugal force on a slide surface bounding the inner circumference of the spinning chamber and diverging in the direction towards the opposite closed end of the same. They move along this slide chamber, still under the influence of centrifugalforce, until they reach anannular withdrawing channel in which the fibers become deposited and form a yarn which is then withdrawn along the axis of rotation of the chamber through an opening provided for this purpose in the closed end thereof.

Experience has shown that the quality of yarn produced in this manner is governed by a variety of considerations and circumstances. These are already well known to those skilled in the art and need not therefore be enumerated here at length. Basically speaking, however, it has been found that particularly crucial aspects appear to be the creation of an optimum sliver configuration the feeding of fibers to this sliver which exists within the spinning chamber, and the twisting of the sliver into a yarn.

According to one type of proposal known from the priorart, the sliver is produced in the aforementioned annular groove which is located at the largest inner diameter of the spinning chamber'and is defined by tapered walls. The sliver thus formed in this groove has the cross-sectional configuration of a common triangle and, it will be understood, is produced in the groove also known as the collecting surface by the incoming fibers due to their gradual deposition at the apex of the longer side of the triangle. It has been found, however,

that it is impossible with this prior art proposal to maintain the similarity of sliver cross-section for different yarn numbers throughout the process of converting the sliver into a yarn by twisting it. Sliver of fibers produced on the collecting surface is flat, with a predominant distribution of the fibers on the slip wall along which the fibers move to the collecting surface. This results in high resistance to twisting and few contacts between the individual fibers in the sliver, and the sliver is removed from the collecting surface in a rather imperfect manner.

Furthermore, the yarn produced by twisting the sliver is discharged at the same side in the aforementioned proposals, at which the fibers are fed into the spinning chamber. As a result of this the yarn comes into contact with the newly arriving incoming fibers and this causes a deterioration of its surface structure.

Furthermore, the sliver being converted into yarn is drawn off the collecting surface in radial direction, very quickly after the sliver is formed thereon, and it has 2, been observed that this does not favorably influence the production of yarn which should utilize a natural twisting tendency of the sliver resulting from existing low axial tension and'in the region of yarn formation. This means that the sliver is twisted more or less by force rather than by its natural tendency.

The operation of this prior-art proposal causes the axial tension in the region of yarn formation, that is conversion of sliver into twisted yarn, to be low and because of this, and also due to the circumstance that the twisting process is exacting from the view point of the necessary twisting moment, increased torsional force must be imparted to the sliver to insure that a sufficient twisting moment is imparted to it. This, on the other hand, results in the formation of overtwisted yarn which is harder to the touch, and in a reduced rate of production.

The aforementioned disadvantages have of course been realized and attempts have been made to overcome them, and in particular the necessary twisting moment, by creating such a cross-sectional configuration for the sliver as insures the least possible inertial moment. In other words, the sliver cross section should be as close to circular as possible. For this purpose devices are known which attempt to achieve this objective, for instance spinning chambers wherein the collecting surface as seen in axial direction of the spinning chamber is a recess having a V-shaped configuration with the included angle being less than 35. It has been found, however, that this solution has the disadvantage that the yarn is pressed into the recess and becomes seated between the tapered walls of the same. This prevents it from proper turning during twisting, and from regular twists proceeding into the as yet untwisted sliver portion. Also, impurities tend to become settled in this recess, that is impurities which are inherently present in the incoming fibers, and this appears to be very unfavorable for a proper operation of the spinning chamber, aside from the fact that it is difficult to remove the impurities once they have become settled in the recess.

SUMMARY OF THE INVENTION Accordingly, it is a general object of the present invention to overcome the disadvantages of the prior art.

More particularly, it is an object ofthe present invention to provide an improved method of ringless spinning of staple fibers which do not possess the disadvantages of the prior art.

Still more specifically, it is an object of the present invention to provide such a method which permits the sliver cross-section to have a constant optimum shape, and which insures that only a low inertial moment is re quired for the twisting.

An additional object of the invention is to provide such a method in which a reliable transfer of the twisting moment from the yarn that is from the portion of the sliver which is already being twisted into a yarn into the as yet untwisted sliver, is achieved while eliminating contact of the yarn with newly incoming fibers which are being supplied for deposition and adherence to the sliver.

An additional object is to provide an apparatus for carrying out the present method.

In pursuance of these objects and of others which will become apparent hereafter, one feature of the invention resides in a mehtod-of ringless spinning of separated staple fibers which, briefly stated, comprises the steps of providing a rotary spinning chamber having an inner circumference formed "with an annular yarnforming recess surroundingthe axis of rotation of the chamber. Separated staple fibers are admitted into the rotating spinning chamber and there is formed of them in the aforementioned recess a sliver having a cross section of a triangle a shorter and a longer side of which have a ratio of between l 1.5 and l 5. The sliver thus formed is withdrawn during rotation of the spinning chamber, initially along an inner surface of the chamber and thereupon along the axis of rotation thereof, so that during such withdrawing the sliver becomes twisted due to its rotation with the chamber relative to the section being withdrawn, as well as due to friction with thesurface and thus becomes converted into a yarn.

This withdrawal of the yarn takes place at a side or end of the spinning chamber which is opposite that at which the incoming fibers are admitted, so that the fibers cannot come in contact with the yarn and the disadvantages arising in the prior art from such contact are avoided.

The length of the section representing the projection of the length into the axial section of the chamber over which length the sliver is twisted, fed and transformed into yarn on the draw-ofi wall, compared with the length of the longer side of the triangle constituting the cross-section of the sliver, should have advantageously a ratio of between l 2 and 4 I. r

The distance of the point or region where the yarn leaves the draw-off wall to a plane passing transverse to the axis of rotation of the chamber through the juncture or transition between the drop wall and the drawoff wall, advantageously equals between 1 and 5 times the longer side of the triangular cross-section of the sliver, and the yarn advantageously will leave the drawoff wall at a distance of between I and 7 mm., from the margin of the sliver at the draw-off wall.

The spinning chamber for carrying out the novel method may, according to one embodiment and stated briefly, comprise a cupshaped rotary chamber having an open side and an axially spaced closed side, both extending in planes transverse to the axis of rotation of the chamber. An inner circumferential slip wall is provided in the chamber extending and diverging from the open toward the closed side for slipping of fibers deposited thereon under the influence of centrifugal force. A drop wall extends from the slip wall towards the closed side and diverges further in the direction thereof, and a draw-off wall extends from the drop wall to the'closed side and convergesin the direction thereof.

Advantageously, a plane normal to the axis of rotation and passing through the transistion between the 'drop wall and the draw-off wall will include with the drop wall an anglein the range between substantially 40 and 70, whereas with the draw-off wall it will iniiidififigie within and 20.

It is also advantageous if in axial direction of the spinning chamber thelength of the drop wall will have a ratio with respect to the length of the draw-off wall of l H to l :8.

The transition from the drop wall to the draw-off wall will in axial direction of the rotary spinning chamber and advantageously have a radius amounting to 0.! to 1.8 mm.

It is advantageous to provide. a withdrawal tube which extends through the closed end of the spinning chamber from the interior to the exterior thereof and through which the twisted yarn is withdrawn axially of the spinning chamber, with this withdrawing tube or discharge tube advantageously being adjustable in the direction of rotation of the spinning chamber.

With the method and apparatus according to the present invention the sliver, instead of having to be twisted under considerable application of force, will simply be rolled together with a much smaller force requirement. The cross section of the sliver is optimum with respect to the direction of the drawing-off of twisted yarn, and thus the requirement for the yarn twisting moment can be reduced while improving the transition of twist into the sliver on the collecting surface of the spinning chamber. This helps to reduce the number of yarn twists and, in consequence, improves the productivity of the'apparatus. On the other hand, the cleaning of the collecting surface from accumulating impurities is quite easy especially in view of the fact that particles and impurities do not tend to adhere to it and at most will do so only very sparsely.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is an axial section through a spinning chamber according to the present invention:

FIG. 2 is a fragmentary axial section of the spinning chamber in FIG. I,on an enlarged scale showing the sliver formed therein in cross-section;

FIG. 3 is a view similar to FIG. 2, but illustrating the rolling of the sliver into yarn by twisting;

FIG. 4 is a view of a portion of the developed walls of the interior of the spinning chamber, and showing the rolling of the sliver into yarn;

FIG. 5 is a view similar to FIG. 4,'illustrating one embodiment of the inclination of the drop wall;

FIG. 5a is a view similar to FIG. 5 illustrating a further embodiment of the inclination of the drop wall;

FIG. 6 is a view similar to FIG. 5, but illustrating one embodiment of the inclination of the draw-off wall;

FIG. 6a is a view similar to FIG. 6 and illustrating a further embodiment of the inclination of the draw-off wall; and

FIG. 7 is an axial sectional view taken on a plane normal to the plane of FIG. I.

' DESCRIPTION OF THE PREFERRED EMBODIMENTS an open side which is provided with the intake opening I2 and a closed side or bottom wall 16 on the exterior of which there is provided the shank 11 and a pulley 17 by means of which via the agency of a drive belt 5 rotation is transmitted to the spinning chamber 1.

In the interior the spinning chamber 1 is provided with a circumferentially extending slip wall 13 which diverges towards the closed side 16 and merges into a drop wall 14 that diverges further in the direction towards the closed side 16 and at a greater angle than the slip wall 13. The drop wall 14 in turn merges with the draw-off wall 15 which extends to the closed side 16 and converges also in the direction towards the same.

A stationary outlet tube 23 extends into the shank 11 and has an end which projects into the cavity of the spinning chamber 1, being provided with an inlet opening 230 through which yarn is withdrawn from the spinning chamber. The opposite outer end of the tube 23 extends beyond the shank and is secured to the stationary part 2 of the machine, advantageously being adjustable in the direction of rotation of the spinning chamber.

A removable cover 3 is provided which overllies and closes the intake opening 12 of the spinning chamber 1, but in such a way as not to contact the latter, because the cover is stationary. The cover 3 may form a part of a non-illustrated separating'device for separating fibers supplied to it, and such a device is knownper se to those skilled in the art.

lt is advantageous and currently preferred, if as shown in FIGS. 6 and 6a, the plane 18 passing in direction normal to the axis of rotation of the spinning chamber through the transition from the drop wall 14 to the draw-off wall 15, will include with the latter or rather that the general plane of the latter an angle A ranging between substantially 40 and 70, as illustrated in FIGS. 6 and 6a.

lt is further advantageous for the general plane of the drop wall 14 to include with thesame plane 18 mentioned above an angle B which is within the range of- 30 (FIG. 5) and (FIG. 5a).

Also. it is advantageous. if, seen in axial direction of the spinning chamber, the ratio of the length ofthe wall 14 to the length of the wall 15 is within the range of l :l.landl:8.

Furthermore, it is advantageous for the radiusR of the transition between the wall 14 and the wall 15 to be between 0.1 and L8 mm.

It will also be seen that the cover 3 is provided with a channel 31 so oriented with respect to the slip wall 15 as to deposit incoming fibers thereon, the fibers being identified with reference numeral 6. A pair of withdrawing rollers 41 and 42 are arranged downstream of the tube 23, at least one of these rollers being driven so that they can withdraw the finished yarn from the interior of the chamber through the tube 23.

lt will be appreciated that the chamber 1 can be operated without any means for producing negative or underpressure in its interior as illustrated, rather it can be provided with such means both approaches being already known from the art. Such negative pressure can be produced by forming the wall of the spinning chamber eithe with openings through which air is ejected centrifugally during rotation or by connecting the interior of the spinning chamber with an external source of underpressure.

ln operation the separated fibers 6 are supplied to the interior of the chamber 1 via the channel 31 from the non-illustrated known separating unit, for instance by being carried along in a stream of air. They become deposited on the slip wall 13 and due to the effective centrifugal force they will slip along the wall l3'(hence the term slip wall) to the drop wall l4.-At the drop wall they will fall and will become deposited onto the collecting surface formed by a part of the drop wall 14 and a part of the draw-off wall 15. On this collecting surface, the fibers will form a sliver 61 within the circumferential region of the collecting surface over which the sliver 61 is in contact with the walls 14 and 15. it will be appreciated that the drop wall 15 in particular is of essential importancefor formation of a sufficiently narrow sliver 61 which latter is produced by deposition of the fibers 6 which become in effect superimposed on one another and adhere together.

The sliver 61 forming on the collecting surface has a cross-section which at least approximates the shape of a triangle the shorter side a of which, in contact with the drop wall 14, will preferably have a ratio of l 1.] to l 5 with respect to the longer ide b which is in contact with the draw-off wall 15.

The sliver 61 becomes converted into yarn 62, and in particular it is rolled up to form this yarn in such a way that the sliver is guided over a certain distance d along the wall 15 under the effect of centrifugal force. The frictional force thus generated between the wall 15 and sliver 61 which is being rolled together, exerts an additional twisting moment during therelative movement of sliver and wall 15, helping the sliver 61 to'roll together and form the yarn 62. The yarn 62 will bend at point B in the direction towards the opening 230 through which it is discharged from the chamber 1.

As FIGS. 1 and 7 show particularly clearly, the yarn 62 has the form of a space curve from the point of its formation to the opening 230. As a result of the drawoff velocity the speed U of the yarn 62 (see in particular FIG. 7) exceeds the rotational speed of the spinning chamber 1 in the direction S. The relative speed of the spinning chamber 1 with respect to the yarn 62 being formed can, in consequence, be determined. The yarn 62 is pressed against the rotating wall 15 under the effect of centrifugal force up to the point P. Because of the relative speed between the yarn 62 and the spinning chamber 1, and the simultaneous influence of the force with which the yarn 62 is pressed against the wall 15, a friction is generated which produces sufficient twisting moment in yarn 62, corresponding in its direction with the sense of rolling of the sliver 61, to support the process of rolling the sliver together. This means that the twisting moment imparted to the sliver 61 on the collecting surface is increased by this twisting moment generated by the frictional force.

The relative speedof the spinning chamber 1 with respect to the yarn 62 diminishes along with the increasing distance from the collecting surface towards the axis of rotation. To insure optimum conditions of the spinning process it is therefore appropriate to maintain the distance of the last point of contact P of the yarn 62 with the wall 15, from the plane 18 within the limits of between 1 and 4 times the length of the longer side b of the triangular cross section of the sliver.

The converted yarn 62 is drawn off from the chamber 1 through the outlet tube 23 by the rollers 41 and 42 and is then wound up by a non-illustrated winding mechanism, which forms no part of the invention and is known per se.

. 7 The length of the section M (see FIG. 7), as the axial section projection of the length d over which the sliver 61 isrolled, guided and converted into yarn 62 on the draw-off wall 15, advantageously will have a ratio'of between 1': 2 and 4 l, relative to the length of the longer side b of the triangular cross section of the sliver 61- The yarn 62 should desirably leave the wall within a distance of between substantially 2 and 7 mm. from the edge or margin of the sliver 61 at the draw-off wall 15, and the shape of the draw-off wall 15, as seen in axial direction of the spinning chamber 1, may be convex, concave, direct, broken or it may be a combination of these configurations.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

While the invention has been illustrated and described as embodied in the ringless spinning of staple fibers, it is not intended to be limited to the details shown, since various modifications and structural changes may be madewithout departing in any way from the spirit of thepresent invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge readily adapt it for various applications without omitting features that from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What isclaimed as new and desired to be protected by Letters Patent is set forth in the appended claimsi l. A method of ringless spinning of separated staple fibers, comprising the steps of providing a rotary negative pressure spinning chamber having an axial inlet end and an opposite axial outlet end and an. inner circumference provided with an annular yarn-forming recess surrounding the axis of rotation of said chamber intermediate said ends and formed by a slip wall diverging from said inlet end to said recess, a drop wall diverging further from said slipwall in radially outward direction and toward said outlet end, and a draw-off wall converging from-said drop wall towards said outlet end and inclined relative to said drop wall at a ratio of between l:l.5 and 1:5; admitting separated staple fibers into the rotating spinning chamber and forming of them in said recess a sliver having the cross-section of a triangle the-shortest and a longer side of which have a ratio of between l:l.5 and 1:5 and said shortest side of which lies against said drop wall whereas said longer side lies against said draw-off wall while a further side of said triangle faces radially inwardly of said chamber; and withdrawing said sliver during rotation of said chamber initially along said draw-off wall of said chamber and thereupon along the axis of rotation thereof and through said outlet end, so that during such withdrawing the .sliver becomes twisted due to its rotation with said chamber relative to the sliver section being withdrawn, and becomes further twisted due to friction with said draw-off wall, and thus becomes converted into a yarn.

2. A rotary spining chamber for ringlessspinning of separated staple fibers, comprising a cup shapedioYary chamber having an open side and an axially spaced closed side provided with an outlet, both of said sides extending in planes transverse to the axis of rotation of said chamber; an inner circumferential slip wall extending and diverging from said open side radially outwardly and toward said closed side for slipping of fibers deposited thereon under the influence of centrifugal force; a drop wall extending from said slip wall towards said closed side and diverging further radially outwardly and in the direction of said closed side and a draw-off wall forming a junction with said drop wall afiaeneaaing from said'drop w all iasai'a cl osedside and converging in the direction thereof, said draw-off wall defining with said drop wall a sliver-forming groove having a crosssection resembling a triangle the shortest and a longer side of which have a ratio of be tween 1 1.5 and l :5 and of which said shortest side is formed by said drop wall and said longer side is formed by said draw-off wall, so that sliver formed in said groove will have a corresponding cross-sectionof a triangle a further side of which faces radially inwardly of said chamber while said shortest and longer sides respectively lie on said drop wall and said draw-off wall whereby, when said sliver is initially withdrawn along said draw-off wall and thereupon along said axis of rotation and through said outlet, said sliver becomes twisted due to its rotation with said chamber relative to the sliver section which is being withdrawn, and becomes further twisted due to friction with said draw-off wall.

3. A method as described in claim I, said annular recess being bounded by a drop wall and a draw-off wall which are mutually inclined at said ratio.

4. A method as defined in claim 3, said chamber having an axial end through which said yarn is withdrawn, and said draw-off wall being at a side of said recess which is closer to said axial end than said drop wall, with said longer side of said triangle being located on said draw-off wall.

5. A method as defined in claim I, wherein the length of an axial section representing the length over which sliver is twisted and converted into yarn on said drawoff wall has aratio of between 1 :-2 and 4 l with reference to said longer side of said triangle.

6.A'method as defined in claim 1, wherein the distance between a point of said draw-off wall at which said sliver is lifted off the latter and a plane of separation of said drop wall and said draw-off wall equals between 1 and 3 times the length of said longer side of said triangle.

7. A method as defined in claim 1, wherein the distance between a point of said draw-off wall at which said sliver islifted ofi the latter and a lateral margin of sliver in said recess is between 1 and 4 mm.

8. A rotary spinning chamber as defined in claim 2, wherein an imaginary plane normal to the axis of rotation of said spinning chamber and passing through the junction of said drop wall and draw-off wall defines with the general plane of the former wall an angle of between 30 and 20, and with the general plane of the latter wall an angle of between 40 and 9. A rotary spinning chamber as defined in claim 2, wherein the length of said drop wall in axial direction of said chamber relative to the length of said draw-off wall has a ratio of between 1 Li and l 8.

10. A rotary spinning chamber as defined in claim 2, wherein said drop wall merges with said draw-off wall said chamber.

12. A rotary spinning chamber as defined in claim 1 1, wherein said withdrawing tube is at least in part adjustable in direction of rotation of said chamber. 

1. A method of ringless spinning of separated staple fibers, comprising the steps of providing a rotary negative pressure spinning chamber having an axial inlet end and an opposite axial outlet end and an inner circumference provided with an annular yarn-forming recess surrounding the axis of rotation of said chamber intermediate said ends and formed by a slip wall diverging from said inlet end to said recess, a drop wall diverging further from said slip wall in radially outward direction and toward said outlet end, and a draw-off wall converging from said drop wall towards said outlet end and inclined relative to said drop wall at a ratio of between 1:1.5 and 1:5; admitting separated staple fibers into the rotating spinning chamber and forming of them in said recess a sliver having the cross-section of a triangle the shortest and a longer side of which have a ratio of between 1:1.5 and 1:5 and said shortest side of which lies against said drop wall whereas said longer side lies against said draw-off wall while a further side of said triangle faces radially inwardly of said chamber; and withdrawing said sliver during rotation of said chamber initially along said draw-off wall of said chamber and thereupon along the axis of rotation thereof and through said outlet end, so that during such withdrawing the sliver becomes twisted due to its rotation with said chamber relative to the sliver section being withdrawn, and becomes further twisted due to friction with said draw-off wall, and thus becomes converted into a yarn.
 2. A rotry spinning chamber for ringless spinning of separated staple fibers, comprising a cup-shaped rotary chamber having an open side and an axially spaced closed side provided with an outlet, both of said sides extending in planes transverse to the axis of rotation of said chamber; an inner circumferential slip wall extending and diverging from said open side radially outwardly and toward said closed side for slipping of fibers deposited thereon under the influence of centrifugal force; a drop wall extending from said slip wall towards said closed side and diverging further radially outwardly and in the direction of said closed side and a draw-off wall forming a jucntion with said drop wall and extending from said drop wall to said closed side and converging in the direction thereof, said draw-off wall defining with said drop wall a sliver-forming groove having a cross section resembling a triangle the shortest and a longer side of which have a ratio of between 1:1.5 and 1:5 and of which said shortest side is formed by said drop wall and said longer side is formed by said draw-off wall, so that sliver formed in said groove will have a corresponding cross-section of a triangle a further side of which faces radially inwardly of said chamber while said shortest and longer sides respectively lie on said drop wall and said draw-off wall whereby, when said sliver is initially withdrawn along said draw-off wall and thereupon along said axis of rotation and through said outlet, said sliver becomes twisted due to its rotation with said chamber relative to the sliver section which is being withdrawn, and becomes further twisted due to friction with said draw-off wall.
 3. A method as described in claim 1, said annular recess being bounded by a drop wall and a draw-off wall which are mutually inclined at said ratio.
 4. A method as defined in claim 3, said chamber having an axial end through which said yarn is withdrawn, and said draw-off wall being at a side of said recess which is closer to said axial end than said drop wall, with said longer side of said triangle being located on said draw-off wall.
 5. A method as defined in claim 1, wherein the length of an axial section representing the length over which sliver is twisted and converted into yarn on said draw-off wall has a ratio of between 1 : 2 and 4 : 1 with reference to said longer side of said triangle.
 6. A method as defined in claim 1, wherein the distance between a point of said draw-off wall at which said sliver is lifted off the latter and a plane of separation of said drop wall and said draw-off wall equals between 1 and 3 times the length of said longer side of said triangle.
 7. A method as defined in claim 1, wherein the distance between a point of said draw-off wall at which said sliver is lifted off the latter and a lateral margin of sliver in said recess is between 1 and 4 mm.
 8. A rotary spinning chamber as defined in claim 2, wherein an imaginary plane normal to the axis of rotation of said spinning chamber and passing through the junction of said drop wall and draw-off wall defines with the general plane of the former wall an angle of between - 30* and + 20*, and with the general plane of the latter wall an angle of between 40* and 70*.
 9. A rotary spinning chamber as defined in claim 2, wherein the length of said drop wall in axial direction of said chamber relative to the length of said draw-off wall has a ratio of between 1 : 1.1 and 1 :
 8. 10. A rotary spinning chamber as defined in claim 2, wherein said drop wall merges with said draw-off wall on a radius which in axial direction of said chamber amounts to between 0.1 and 1.8 mm.
 11. A rotary spinning chamber as defined in claim 2; further comprising a withdrawing tube extending through said outlet from the interior to the exterior of said chamber.
 12. A rotary spinning chamber as defined in claim 11, wherein said withdrawing tube is at least in part adjustable in direction of rotation of said chamber. 